Thx for answer i'll check when i back to home, im at work now but: i have another question,:
I tried solution from: how to boot aptosid from usb and used from manual: dd if=/path/to/aptosid-*.iso of=/dev/sdf. Soo i used command dd if=/home/bryn1u/aptosid.iso of=/dev/sdc1 (pendrive). When install finished i wanted to open it and i couldn't. Only changes which i saw, it name of pendrive (from pendrive on aptosid) and nothing else. My usb pendrive doesnt want to boot and i can't open it. I tried with flash disc usb 250 GB segate and the same problem. Any solution ?

For KMS to function in combination with ATi/ AMD radeon graphics, firmware images (firmware-linux-nonfree, see below) are required, which can't be shipped on aptosid live media, while X.org should transparently fall back to vesa on problematic cards, special attention might be needed in rare cases. If X doesn't manage to start on ATi/ AMD radeon graphics cards, it might help to supply "radeon.modeset=0" as boot option for the live CD and to install the required firmware package "firmware-linux-nonfree" on the live system, before installing to the harddisk. Once firmware-linux-nonfree is installed, kernel parameters like "radeon.modeset=0" or "vga=791" should not be used anymore, as they might interfere with KMS operations, which are needed for radeon to work properly.

Or in other words, try adding "radeon.modeset=0" at boot time.

If that doesn't work I think it would be worth trying to see if the output is "just" going to the wrong card (as you say you have two video cards)?